Title: A comparative overview of the Animal Kingdom
1A comparative overview of the Animal Kingdom
2General Features of Animals
- Animals are the consumers of the Earth
- They are a very diverse group
- -However, they share major characteristics
- -Are heterotrophs
- -Are multicellular
- -Have cells without cell walls
- -Most are able to move
3General Features of Animals
-
- -Are very diverse in form and habitat
- -Most reproduce sexually
- -Have a characteristic pattern of
embryonic development - -Cells of all animals (except sponges) are
organized into tissues -
4(No Transcript)
5(No Transcript)
6Evolution of the Animal Body Plan
- Five key transitions can be noted in animal
evolution - 1. Tissues
- 2. Symmetry
- 3. Body cavity
- 4. Development
- 5. Segmentation
7Evolution of the Animal Body Plan
- 1. Evolution of tissues
- -Parazoa (Sponges - the simplest animals) lack
defined tissues and organs - -Have the ability to disaggregate and
aggregate their cells - -Eumetazoa (all other animals) have distinct and
well-defined tissues - -Have irreversible differentiation for most
cell types
8Evolution of the Animal Body Plan
- 2. Evolution of symmetry
- -Sponges also lack any definite symmetry
- -Eumetazoa have a symmetry defined along an
imaginary axis drawn through the animals body - -There are two main types of symmetry
9Evolution of the Animal Body Plan
- -Radial symmetry
- -Body parts arranged around central axis
- -Can be bisected into two equal halves in any
2-D plane - -Bilateral symmetry
- -Body has right and left halves that are
mirror images - -Only the sagittal plane bisects the animal
into two equal halves
9
10(No Transcript)
11Evolution of the Animal Body Plan
- Bilaterally symmetrical animals have two main
advantages over radially symmetrical ones -
- 1. Cephalization
- -Evolution of a definite brain area
- 2. Greater mobility
12Evolution of the Animal Body Plan
- 3. Evolution of a body cavity
- -Eumetazoa produce three germ layers
- -Outer ectoderm (body coverings and nervous
system) - -Middle mesoderm (skeleton and muscles)
- -Inner endoderm (digestive organs and
intestines) - Body cavity Space surrounded by mesoderm tissue
that is formed during development
12
13Evolution of the Animal Body Plan
- 3. Evolution of a body cavity
- -Three basic kinds of body plans
- -Acoelomates No body cavity
- -Pseudocoelomates Body cavity between mesoderm
and endoderm - -Called the pseudocoel
- -Coelomates Body cavity entirely within the
mesoderm - -Called the coelom
13
14(No Transcript)
15Evolution of the Animal Body Plan
- -The body cavity made possible the development
of advanced organs systems - -Coelomates developed a circulatory system to
flow nutrients and remove wastes - -Open circulatory system blood passes from
vessels into sinuses, mixes with body fluids and
reenters the vessels - -Closed circulatory system blood moves
continuously through vessels that are separated
from body fluids
15
16Evolution of the Animal Body Plan
- 4. Evolution of different patterns of development
- -The basic Bilaterian pattern of development
- -Mitotic cell divisions of the egg form a
hollow ball of cells, called the blastula - -Blastula indents to form a two-layer- thick
ball with - -Blastopore Opening to outside
- -Archenteron Primitive body cavity
16
17Evolution of the Animal Body Plan
- Bilaterians can be divided into two groups
- -Protostomes develop the mouth first from or
near the blastopore - -Anus (if present) develops either from
blastopore or another region of embryo - -Deuterostomes develop the anus first from the
blastopore - -Mouth develops later from another region of
the embryo
17
18Evolution of the Animal Body Plan
- Deuterostomes differ from protostomes in three
other fundamental embryological features - -1. Cleaveage pattern of embryonic cells
- -Protostomes Spiral cleavage
- -Deuterostomes Radial cleavage
- -2. Developmental fate of cells
- -Protostomes Determinate development
- -Deuterostomes Indeterminate development
18
19Evolution of the Animal Body Plan
- -3. Origination of coelom
- -Protostomes Forms simply and directly from
the mesoderm - -Deuterostomes Forms indirectly from the
archenteron - Deuterostomes evolved from protostomes more than
500 MYA
20(No Transcript)
21Evolution of the Animal Body Plan
- 5. Evolution of segmentation
- -Segmentation provides two advantages
- -1. Allows redundant organ systems in adults
such as occurs in the annelids - -2. Allows for more efficient and flexible
movement because each segment can move
independently -
- Segmentation appeared several times in the
evolution of animals
21
22Traditional Classification of Animals
- Multicellular animals, or metazoans, are
traditionally divided into 36 or so distinct
phyla based on shared anatomy and embryology - Metazoans are divided into two main branches
- -Parazoa Lack symmetry and tissues
- -Eumetazoa Have symmetry and tissues
- -Diploblastic Have two germ layers
- -Triploblastic Have three germ layers
22
23A New Look At Metazoans
- The traditional animal phylogeny is being
reevaluated using molecular data - Myzostomids are marine animals that are parasites
of echinoderms - -Have no body cavity and only incomplete
segmentation - -And so have been allied with annelids
23
24A New Look At Metazoans
- Recent analysis of the translation machinery
revealed that myzostomids have no close link to
the annelids at all
-Instead, they are more closely allied with the
flatworms (planaria and tapeworms)
25A New Look At Metazoans
- Therefore, key morphological characters used in
traditional classification are not necessarily
conservative - Molecular systematics uses unique sequences
within certain genes to identify clusters of
related groups
25
26A New Look At Metazoans
- Most new phylogenies agree on two revolutionary
features - 1. Separation of annelids and arthropods into
different clades - 2. Division of the protostome group into
Ecdysozoa and Spiralia - -The latter is then broken down into
Lophotrochozoa and Platyzoa
26
27A New Look At Metazoans
28Evolutionary Developmental Biology
- Most taxonomists agree that the animal kingdom is
monophyletic - Three prominent hypotheses have been proposed for
the origin of metazoans from single-celled
protists -
28
29Evolutionary Developmental Biology
- 1. The multinucleate hypothesis
- 2. The colonial flagellate hypothesis
- 3. The polyphyletic origin hypothesis
- Molecular systematics using rRNA sequences
settles this argument in favor of the colonial
flagellate hypothesis
29
30Evolutionary Developmental Biology
- Molecular analysis may also explain the Cambrian
explosion - -The enormous expansion of animal diversity in
the Cambrian period (543 to 525 MYA) - -The homeobox (Hox) developmental gene complex
evolved - -Provided a tool that can produce rapid
changes in body plan
30